The odd moment of honest drama or genuinely witty humour catches us completely off guard, because this is one of those resolutely bland Hollywood star machines that bears no resemblance to the real world at all.

In Atlanta, TV fitness guru Jules (Diaz) is about to reveal that she's pregnant by her celebrity dance show partner Evan (Morrison). Meanwhile, Holly and Alex (Lopez and Santoro) are looking into adoption even though they're not sure they're ready; Wendy and Gary (Banks and Falcone) are finally expecting after trying for years, only to be upstaged by Gary's dad (Quaid) and his much younger wife (Decker); and food truck operators Rosie and Marco (Kendrick and Crawford) rekindle their teen romance with unexpected results.

Based on the Heidi Murkoff's self-help book, this is lazy screenwriting by numbers. Although the cast members manage to inject some personality from time to time, each plot strand is so constrained by the rom-com structure that it has nowhere to go. Surely there'll be one miscarriage, one baby will be an unexpected sex and someone will have childbirth complications. Check. Check. Check. But because of the sunny, sentimental tone, we know everyone will remain smiling.

There's nothing wrong with the performances: this is a strikingly good-looking cast playing watchable people who struggle just a little along their journey into the unknown of parenthood. Jagged comedy is provided by professionals like Rock (as the leader of a baby-walking dads' club) and Megan Mullally (in a sublimely silly cameo as Evan's new dance-competition partner). Meanwhile there's eye-candy for everyone, with all of these outrageously hot moms-to-be, plus the dreamy likes of Santoro, Crawford and Manganiello (in a gratuitously shirtless muscle-man role).

And yes, the movie feels just as assembled as all that, raising a chuckle or tear or gross-out grimmace right on cue. It's like the filmmakers picked every element from a movie-marketing checklist designed to create a more family-friendly Bridesmaids. There's a bit of vulgarity, and very vague hints that someone may have had sex at some point but, beyond one moment of shockingly prejudicial language, the cast and crew seem terrified of letting any actual humanity invade the screen.